Calcium is an absolute requirement for glucose-induced insulin release from the B-cell. Evidence indicates that alterations in intracellular calcium which occur during the insulin secretory process result from changes in the subcellular distribution of calcium by specific subcellular organelles. The objectives of this research project are to study the molecular mechanisms involved in regulating calcium movements by the B-cell plasma membrane and endoplasmic reticulum. Passive calcium binding and ATP-dependent calcium transport will be characterized in these specific subcellular organelles. This will permit evaluation of the effects of agents and conditions which alter insulin release on these calcium dependent parameters. The high affinity calcium stimulated ATPase will be characterized in each organelle to determine if a relationship exists between this enzymatic activity and the calcium ion transport system. The effect of specific trace elements: Zn ions, Cr ions, Cd ions, Fe ions, Cu ions, and Pb ions will be determined on insulin release from isolated islets which will then allow assessment as to whether these agents exert their effect by interfering with the described calcium dependent processes mediated by the plasma membrane and endoplasmic reticulum.